Directly #include required X11/XvMC header.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@17450 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/mpegvideo_xvmc.c

@@ -20,6 +20,7 @@
  */
 
 #include <limits.h>
+#include <X11/extensions/XvMC.h>
 
 #include "avcodec.h"
 #include "dsputil.h"